Process for the preparation of fatty acid alkyl esters having improved processing properties

Abstract

Lower alkyl esters of higher fatty acids with improved processing properties, particularly sulfonation, are obtained by subjecting lower alkyl esters of higher fatty acids of plant and/or animal origin, or said fatty acids per se, in the presence of esterification catalysts and/or carboxylic acid anhydrides, to a brief temperature treatment above 150° C., and separating simultaneously and/or subsequently, preferably by distillation, the purified lower alkyl esters of higher fatty acids or the purified higher fatty acids from the treated material and the purified higher fatty acids are then esterified with lower alkanols.

We claim: 
     
       1. A process for the preparation of sulfonated lower alkyl esters of higher fatty acids comprising the steps of A. subjecting free higher fatty acids of plant and/or animal origin to purification by a heat treatment of from 150° to 280° C. in the presence of an amount of an additive effective to reduce the hydroxyl number of said fatty acids, said additive being selected from the group consisting of esterification catalysts and carboxylic acid anhydrides, for a time sufficient to effect an improvement in a subsequent sulfonation process,   B. separating purified higher fatty acids from the treated material,   C. esterifying the purified higher fatty acids with a lower alkanol under esterification conditions,   D. recovering said lower alkyl esters of higher fatty acids,   E. sulfonating said recovered esters and recovering an α-sulfonated lower alkyl ester of said higher fatty acid which when bleached has a Klett number of 60 or below.   
     
     
       2. The process of claim 1 wherein the heating time is from 0.1 to 60 minutes and the purified higher fatty acids are separated by vacuum distillation at a subatmospheric pressure of from 0.1 to 10 torr.   
     
     
       3. The process of claim 1 wherein the starting free higher fatty acid is an unhardened tallow fatty acid. 
     
     
       4. The process of claim 1 wherein said heat treatment temperature and said heat treatment time are mutually adjusted so that an esterification or reesterification of free hydroxyl groups present in the starting materials takes place without any other substantial change in the structure of said lower alkyl esters of higher fatty acids. 
     
     
       5. The process of claim 2 wherein the esterification catalyst is present in an amount of from 0.01 to 10% by weight of fatty acid starting material and is a basic, neutral, or weakly acid catalyst which is soluble in the starting material. 
     
     
       6. The process of claim 2 wherein the additive is a high boiling carboxylic acid anhydride. 
     
     
       7. A process for the preparation of sulfonated lower alkyl esters of higher fatty acids comprising the steps of A. subjecting free fatty acids of plant or animal origin to purification by a heat treatment at 200° to 250° C. for 0.1 to 60 minutes in the presence of an amount of an additive selected from the group of esterification catalysts and carboxylic acid anhydrides,   B. vacuum distilling the purified free fatty acids at a sub-atmospheric pressure of from 0.1 to 10 torr,   C. esterifying the distilled, purified fatty acids with a lower alkanol under esterification conditions,   D. recovering the lower alkyl esters of higher fatty acids,   E. sulfonating said recovered esters and   F. recovering an α-sulfonated lower alkyl ester of said higher fatty acid which when bleached has a Klett number of 60 or below.   
     
     
       8. The process of claim 7 wherein the starting free higher fatty acid is a tallow fatty acid and the lower alkanol contains from one to five carbon atoms. 
     
     
       9. The process of claim 8 wherein the fatty acid is an unhardened tallow fatty acid and the alkanol is methanol. 
     
     
       10. The process of claim 7 wherein the esterification catalyst used during step A is essentially neutral to alkaline reacting and is soluble in the starting material. 
     
     
       11. The process of claim 10 wherein the additive used in Step 1 is a high boiling carboxylic acid anhydride. 
     
     
       12. The process of claim 7 wherein steps A and B are combined. 
     
     
       13. The process of claim 8 whrein the starting free higher fatty acid is a hardened methyl ester of a tallow fatty acid.